Cutting fluid



Patented May 17, 1949 CUTTING FLUID Hollis L. Leland, Cranford, N. J., assignor to Standard Oil Development Company, a corporation of Delaware No Drawing. Application December 5, 1945, Serial No. 633,053

- and the work in a steady stream and function to dissipate the heat from both the tool and the work; improve the quality of the surface produced; lubricate the surfaces in contact between the tool and work; prevent build-up on the tool or the welding of the work to the tool; to wash away the chips and to provide lubrication between the chips and the tool. For some of the foregoing purposes, such as washing away chips, any fluid will do. For dissipating heat a fluid should be provided having a high specific heat, while for improved quality of surface and long tool life, a

fluid must be provided capable of supplying a high-load-carrying film.

Machining, generally speaking, is a two-stage operation, the roughing out being the first stage and the finishing cut being the second stage. In rough cuts the primary objects is to remove material, and the quality of the surface produced is. secondary. However, since in the following finishing cut only a very small amount of material is removed, the preceding rough out should not leave the work in such a condition that the finishing cut will fail to remove the scars left by the rough out. The effectiveness of a cutting fluid is measured by the amount of metal which can be removed during the roughing cut and yet leave the material in a condition where only a very light finishing cut need be taken. There is normally an enormous pressure between the cutting edge of the tool and the metal being machined, and in addition, due to the inherent resilience of the metal, heavy pressures are maintained between the work and the surface of the tool just over the cutting edge and between the chips and the surface of the tool just back of the cutting edge. Therefore, it is required that a cutting fluid be provided which is capable of maintaining a lubricating film even under heavy loads.

It has heretofore been recognized that the presence of sulfur and sulfur compounds improves the load-bearing characteristics of a cutting fluid.

In furtherance of this idea numerous sulfur compounds and sulfurized oils have been utilized as additives in cutting fluids. In this manner cuttingfluids containing as much as 8 to 10% or more of the sulfur have been developed, although usually such products contain not more than 4 to 5 per cent of sulfur. Sulfurized cutting fluids, however, leave much to be desired in their performance. Sulfur and sulfur compounds stain and corrode many non-ferrous alloys, particularly those alloys containing copper, and even 1 Claim. (Cl. 252-498) some types of iron and steel develop stain and corrosion spots after having been in contact with sulfurized cutting fluids.

Many emulsifiable metal fabricating fluids as emulsions often possess the objectionable feature of not being permanent dispersions in that they are either subject to phase separation on standing for any appreciable time or precipitate out as a sediment a large part of the ingredient present for its load-carrying characteristics. A cutting fluid having high load-bearing characteristics in the form of a stable water-emulsion is therefore quite desirable.

It is therefore an object of the present invention to produce a stable emulsion cutting fluid of high load-carrying ability. Another object is the production of a cutting fluid which will not stain or corrode either ferrous or non-ferrous alloys. These and other objects will be apparent to those skilled in the art upon reading the following description.

It has now been found that by the selection of the proper emulsifier, organic esters of acids such as phosphoric acid, phosphorous acid, thiophosphoric acid, and thiophosphorous acid or mixtures of these esters and mineral lubricating oil can be emulsified with water giving permanently stable emulsions which are useful as cutting fluids. These organic esters of the acids of phosphorus have been recognized as having oiliness or loadbearing characteristics and solutions or suspensions of them have been employed in an attempt to utilize these properties. Esters falling within these two classifications have the most probable formulae:

where X is either oxygen or sulfur and R is either hydrogen, an aliphatic hydrocarbon radical such as methyl, ethyl, propyl, butyl, isobutyl, octyl, decyl, dodecyl, etc.; or an aromatic hydrocarbon radical such as phenyl, cresyl, xylenyl, etc.; at least one of the Rs being a hydrocarbon radical. The emulsifiers found to be particularly adapted to the emulsification of phosphoric, phosphorous, thiophosphoric and thiophosphorous acid esters in water are esters of partially dehydrated hexahydric alcohols in which the esterifying radical contains from 8-30 carbon atoms mixed with the reaction product of the same type of ester and ethylene oxide. Oleic acid ester of partially dehydrated sorbitol is illustrative of the former type of emulsifying agent, and the reaction product of palmitic acid ester of partially dehydrated sorbitol and ethylene oxide is representative of the latter type of emulsifying agent, The reaction product of the ester with ethylene oxide results in a material falling within. the general class of etherester compounds. In making up the emulsifier considerable latitude can be taken with respect to the ratio of ester compound to ether-ester compound. However, according to the present inven-' tion it is preferred to use these materials in the ratios of one part by weight of ester to one to three parts or more by weight of the ether-ester compound.

,The ester types of emulsifying agents employed in the present invention are carboxylic acid esters of partially dehydrated aliphatic polyhydric alcohols such as the hexitols. Partial dehydration converts the polyhydric alcohol to an epoxide or inner ether type of compound having hydroxyl substituents and either one or two mono-oxy, 4-!

chemical figuration. In the case of sorbitol, monodehydration forms a sorbitan, whereas didehydration yields a sorbitide. The hydroxyl groups attached to the-inner ethers still retain the typical reaction of an alcohol, one bf which is that of reaction with a fatty acid to produce an ester. The esterificationof one or more hydroxyl groups in the partially dehydrated polyhydric alcohol yields esters found to be useful for the purposes of the present invention. The acids useful for theesterification of the cyclic etheralcohol compounds, are those fatty acids which are present combined with glycerine in naturally occurring animal and vegetable oils and fats and which are derived therefrom upon saponification membered carbon-oxygen rings in its probable reaches the desired stage. It is frequently detion of the esters formed or the reaction may be carried out in a refluxing hydrocarbon solvent, with means provided for trapping out the water formed.

The ether-ester type of emulsifier is made by reacting an ester produced as above-described with an olefin epoxide such as ethylene oxide in the following manner.

The ester and 1-5% chloride, are placed in a kettle or other container equipped with an suitable agitating device and means of pooling the reaction mixture to prevent the temperature rising above the boilin point of the olefin epoxide used. The desired amount of olefin epoxide is then adding slowly with stirring, about one to two mols of olefin epoxide being used for each mol of ester. After about one hour thereaction is substantially complete. The catathereof and are exemplified by the fatty acids derived from stearin, whale oil, menhaden oil,

' neatfs-foo't oil, castor oil, corn oil, cottonseed oil,

coconut oil, linseed oil, palm kernel oil, rapeseed oil, China-wood'oil, perilla oil, soya bean oil, sunflower oil, olive oil and the like and includes fatty acids, such as caproic, capryllic. capri-c, lauric myristic, palmitic, oleic, linoleic, linolenic, ricinoleic, stearic, dihydroxystearic, eleostearic, erucic, and behenic. Also fatty acids such as synthetically prepared aliphatic monocarboxylic fatty acids, as for instance margaric or fatty acids prepared by suitably oxidizing hydrocarbons or by hydrogenating naturally occurring fatty acids, may be used. The naphthenic acids recovered from certain petroleum oils are also eminently satisfactory. It is also contemplated that mixtures of the foregoing acids may be used in the esterification of the partially dehydrated polyhydric alcohols.

The esters are made by reacting 1 mol of the polyhydric alcohol or 1 mol of the partially dehydrated alcohol with one to three mols of carboxylic acid or carboxylic acid mixtures either in the presence of or absence of a catalyst. The catalyst may be acidic, for example, sulfur 1c or phosphoric acid, or alkaline, like sodium hydroxide. The ingredients are comingld and heated in a kettle or other container, preferably closed and equipped with suitable agitating means at a temperature of 150-300 C. until the reaction lyst may then be conveniently removed by water washing or by the use of an'absorbent medium such as fullers earth.

In making up cutting fluid emulsions, from 01-15% or more, being weight per cent based upon the total composition, of the phosphorus compound, will be used, and from 2-10 weight per cent of the emulsifier, the remainder of the cutting fluid being water. The emulsion is made by first thoroughly mixing the phosphorus compound with the emulsifier, heating if necessary to get an intimate mixture and then incorporating this mixture in water by means of stirring or other mechanical agitation. An emulsion stable over long periods of time is thus obtained.

In cases where the ester portion of the emulsifier is a material with a melting point above room temperature,= such as occurs in the case of the ester of-stearic acid, it may be necessary to form the'cutting fluid by incorporating the homogeneous concentrate at 140 F.-150 F. in a small amount of water heated to a temperature above the melting point of the ester to form a concentrated emulsion. This concentrated emulsion can then be diluted with either hot or cold water to stgengtl vogh Almen Test rage 1 out Emulsion Separation Gradual Loading Shock Loading Hours 2%Tricresyl phosphate, 2% Emulsifler l 2% Emulsifier. 94% Water 24 Carries 15 wts Carries 15 wts. 10% Tncresyl phosihate, 2.5% Emulsliier, 2.5% Emulsiiler Water. 24 do Do. 2% Tricresyl phosp ate, 2% Emulslfler, 2% E er, 94 a Wate 24 15 weights.

10% Mineral Oil Concentrate, Water.

l Oleic acid ester of partially dehydrated sorbitol. 9 Reaction product of palmitic 3 Laurie acid ester of partially dehydrated sorbito 4 Reaction Mineral o (40 seconds Via. at 210 F.)

roduct of olelc acid ester of partially dehydrated scrbitol and eth 9.6% sodium sulfonate and 2.9%

acid ester of partially dehydrated sorbitol and ethylene oxide.

lene oxide. um naphthenate.

of a catalyst such as stannic' hydrated sorbitol 1S1 Reaction In the present invention mineral oils can also be used in conjunction with the phosphorus compounds to give a highly effective cutting fluid oi! the soluble oil type. A wide range of lubricating oils may be employed as the base for the cutting fluid or soluble oil, and, in general, the base oil will comprise an oil having a viscosity at 100 F. in the range of from about 90-500 seconds, an A. P. I. gravity of 23-.-33 and a flash point above 300 F. However, in preparing the compositions of the present invention it is preferred to use a light coastal oil as a' base, that is one having an A. P. I. gravity in the range of 25-31 and a viscosity at 100 F. of from 100-300 seconds.

As will be explained subsequently, the mineral oil, phosphorus compound and emulsifier are first blended into a concentrate which will easily emulsify in water to give a permanent emulsion. The

mineral lubricating oil will compose from -80 weight per cent of the concentrate, which, since it is contemplated using approximately 10 parts of concentrate in parts of water, will result in a water emulsion containing from 6-8 per cent of mineral oil. In the event that mineral lubricating oil is included in the cutting fluid, it has been found necessary to use asthe emulsifier those ester and ester-ether blends in which the ratio of ether-ester to ester is in the upper portion of the range previously indicated, that is to say the ratio of ether-ester to ester will be in the sion has drained off, allowing the turnings to neighborhood of 3 parts or more of ether-ester to 1 part of ester. Also when flcluding oil in the composition particular caremust be taken in compounding the ingredients in order that a permanent emulsion will result.

A permanent emulsion can be secured by flrst' placing the phosphorus compound, emulsifier, and oil in a kettle equipped with a stirrer and heating while stirring to F. The stirring and heating are continued until a homogeneous solution is obtained. If in following this procedure difficulty is encountered in attaining homogeneity, a trace of water may be added as a solubilizer and a homogeneous solution will result. The solution thus formed can be, with or without cooling, stirred into water to yield a permanent emulsion. Ordinarily 10 parts by weight of the solution is incorporated in 90 parts by. weight of water to give a cutting fluid although more cries of the solution can be employed in accordance with the needs of the particular cutting operation.

The following data illustrate the load-carrystand for 24 hours and noting the extent of corrosion at the end of that period. The emulsion is heated to F. before being poured into the crucible. In the present series of tests extremely dilute emulsions were used for the pur-,

pose of accentuating any tendency on the part of the emulsions to corrode iron or steel. The results obtained were as follows:

Gooch cruciblecorrosion test Water/Cutting Oil Ratio Emulsion Base 50/1 100 1 60/1 100/1 60/1 10011 On Cast 0n Malle- 0n Iron able Iron Steel Mineral Oil Concentrate a 3 a 4 o o 10% 'Iricresyl phosphate, Emulsifier, 15% mulsifier, 70% Minera] 01] (40 Sec. Vis. at 210 F.) 3 3 3 4 1 1 Mineral oil (40 seconds Vis. at 210 F.) plus 9.5% sodium sulionate and 2.9% sodium naphthenate.

1 Oleic acid ester of partially dehydrated sorbitol.

1 Reaction product ofpalmltic acid ester of partially dehydrated sorbitol and ethylene oxide.

ing capacity 01' emulsions which contain mineral lubricating oil.

Almen Test Emulsion Gradual Shock Loading Loading Wtl. Wit.

Control 1 3 107 Concentrate AKWV Water 15 15 1 a Concentrate B. 00% Water 15 tially deh drated sorbitol and ethylene oxide, 10% Mineral oil (40 i a??? T3 at i n 'u to 4 8% Lauri acid ester of partial! era: 0! 8 0 o y p groduct of oleic acid deester can dehydrated me :01 and et ylene oxide, 01.5% Miner l 40 nds Vis. at 210 n).

Norm-The Aimui tent no conducted an doeu'ibedinU. 8. Patent 2,001,90l,illuedto3.0.Almon.

fN0 lr-'0=N0 rust, 1==Trace of rust, 2, 3 and 4-increasing extent 0 ms HOLLIS L. LELAND.

REFERENCES crrnn The following references are of record in the the of this patent: ,1

UNITED STATES PATENTS Number Name Date 2,245,649 Caprio June 17, 1941 2,328,540 Hochwalt Sept. 7, 1943 2,402,373 Cordero June 18, 1946 OTHER REFERENCES "spans and Tweens, publication of Atlas Powder 00., 1942, pages 1-16. 

